Rainshine's actual energy consumption for 2010, the first full year of occupied operation, is remarkable.

The 2008 HERS (Home Energy Rating System) rating projected only a 57% improvement over code for RainShine. Not pleased with the HERS rating we chose to conduct our own calculations and projected usage averaging $71.22 per month, an 80% improvement over a code compliant house.

We were confident in our numbers and knew HERS did not consider a variety of factors contributing to energy consumption. Among them:

1. The microclimate of the house

2. The extensive passive solar feature such the overhanging eaves, light shelves and east/west windows located to reduce solar gain through screening from existing trees.

3. The critical factor of the willingness of the clients to live a sustainable life in a sustainable house.

To prove our calculations we tracked the house's actual occupied energy consumption and photovoltaic production for 2010. Average gross utility cost per month was $48.57, an 85% improvement over code. A few more photovoltaic panels and the house would be net zero.

The most disappointing result from our survey was photovoltaic production. Our calculations were based on a site specific calculation provided by the manufacturer who estimated (conservatively according to them) generation of 7,500 kWh/yr. Only 3,155 kWh were generated in 2010, less than half of the projection and a shortfall of $740 for the year and an average of $60 per month. If the PVs had performed up to snuff the house would easily be net zero.

Conclusion: energy projections can be, as we all know, misleading and every house should be tracked to determine actual energy consumption. In general we were delighted with Rainshine's real-life performance. Rainshine proves how energy efficient thoughtfully combining site features, orientation, passive solar design concepts with active systems can be (even when incorporating major areas of glass). Kudos to the owner and design team!

Throwing features and systems at house designs in order to improve energy performance is, as I suspect HERS is necessarily dumbed down to do, wasteful and counterproductive. As in Rainshine an energy efficient house should look like an energy efficient house, not a neo-eclectic mishmash with energy features screwed in/tacked on a sideways compromising manner.

Monday, April 15, 2013

Goal 2 - Extend the times of the year when the house can use natural ventilation instead of heating and cooling

Stack effect with operable clerestory windows

Thru house ventilation

LEED Innovation Credit :

EA 1.2 Innovation
in Architecture - Natural Ventaiation and Cooling

Documentation and
Verification: In the primary
living areas natural ventilation is achieved as follows:

Over 12% in operable
window area/conditioned floor area in the Master Bedroom in addition to a pair
of screened French doors to a covered deck.

Over 12% operable
area/conditioned floor area in the remaining primary living areas (Living Room,
Dining Room, Kitchen, Bed Rooms).
Operable area achieved through inclusion of one door to the Living Area
to the Screened Porch.